Angiotensin-(1-7) potentiates the coronary vasodilatatory effect of bradykinin in the isolated rat heart

It has been shown that angiotensin-(1-7) (Ang-(1-7)) infusion potentiates t he bradykinin (BK)-induced hypotensive response in conscious rats, The pres ent study was conducted to identify Ang-(1-7)-BK interactions in the isolat ed rat heart perfused according to the Langendorff technique, Hearts were e xcised and perfused through the aortic stump under a constant flow with Kre bs-Ringer solution and the changes in perfusion pressure and heart contract ile force were recorded. Bolus injections of BK (2.5, 5, 10 and 20 ng) prod uced a dose-dependent hypotensive effect. Ang-(1-7) added to the perfusion solution (2 ng/ml) did not change the perfusion pressure or the contractile force but doubled the hypotensive effect of the lower doses of BK. The BK- potentiating Ang-(1-7) activity was blocked by pretreatment with indomethac in (5 mg/kg, ip) or L-NAME (30 mg/kg, ip), The Ang-(1-7) antagonist A-779 ( 50 ng/ml in Krebs-Ringer) completely blocked the effect of Ang-(1-7) on BK- induced vasodilation. These data suggest that the potentiation of the BK-in duced vasodilation by Ang(1-7) can be attributed to the release of nitric o xide and vasodilator prostaglandins through an Ang-(1-7) receptor-mediated mechanism.